a) Field of the Invention
The present invention relates to a new or improved internal combustion engine carburetor. Such carburetors typically include a level-controlled system for the fuel in the fuel bowl, and with a control system for the pressure within the fuel bowl.
b) Description of the Prior Art
In conventional carburetors, in which the pressure within the fuel bowl corresponds at least essentially to the induction pressure in the area of the inlet end of the air flow passage because of the fact that the fuel bowl is vented, the mixture ratio depends mainly on the ratio of the specific weights of air and the fuel in a given design and for a specific load. Since the specific weight, and thus air density, changes with altitude, whereas the specific gravity of the fuel does not, the mixture ratio of such a carburetor will vary as a function of altitude and the fuel/air mixture will become richer as altitude increases. In order to compensate for this enrichment, it is known that the pressure within the fuel bowl can be reduced as a function of air pressure, so that the pressure differential between the internal pressure in the fuel bowl and the reduced pressure in the venturi throat where the fuel delivery line opens out (which governs fuel flow) is reduced. A disadvantage in this known system to control the pressure within the fuel bowl by means of a barometric chamber is that it does not take into account the differential between the induction pressure in the area of the inlet end of the air flow passage and the reduced pressure in the area of the venturi throat, which changes as a function of load and engine speed and determines the throughput of air; this makes it more difficult to achieve precise correction of the mixture ratio for altitude, particularly in the partial-load range. In addition, the effects of temperature are not taken into account.